The arrival of the Europeans in the New World in the late 1400s led to the demographic collapse of Native Americans, shows a large-scale study of ancient DNA of pre-Columbian mummies and skeletons between 500 and 8,600 years old.
Diseases brought by Europeans could be one of the reasons for the collapse, according to the researchers.
Published in the journal Science Advances, the study revealed a striking absence of the pre-Columbian genetic lineages in modern indigenous Americans -- showing extinction of these lineages with the arrival of the Spaniards.
"Surprisingly, none of the genetic lineages we found in almost 100 ancient humans were present, or showed evidence of descendants, in today's indigenous populations," said joint lead author Bastien Llamas from University of Adelaide's Australian Centre for Ancient DNA (ACAD).
The researchers examined many demographic scenarios to try and explain the pattern.
"The only scenario that fit our observations was that shortly after the initial colonisation, populations were established that subsequently stayed geographically isolated from one another, and that a major portion of these populations later became extinct following European contact," Llamas said.
gThis closely matches the historical reports of a major demographic collapse immediately after the Spaniards arrived in the late 1400s," Llamas noted.
The research team, which also includes members from the University of California at Santa Cruz (UCSC) and Harvard Medical School, studied maternal genetic lineages by sequencing whole mitochondrial genomes extracted from bone and teeth samples from 92 pre-Columbian - mainly South American - human mummies and skeletons.
The researchers found that the ancient genetic signals also provide a more precise timing of the first people entering the Americas--via the Beringian land bridge that connected Asia and the north-western tip of North America during the last Ice Age.
"Our genetic reconstruction confirms that the first Americans entered around 16,000 years ago via the Pacific coast, skirting around the massive ice sheets that blocked an inland corridor route which only opened much later," professor Alan Cooper, director of ACAD, said.
"They spread southward remarkably swiftly, reaching southern Chile by 14,600 years ago," Cooper pointed out.
